Well they seem to have improved some things with K-3 shutter, damping the movement...maybe they have done same with 645 II so it would be more stable to shoot even with whopping 4 FPS. It would be overkill thou. They also have made some really nice things with K-3 which could be made bigger to allow larger files and faster buffer too... So nobody knows for sure.

There are technology called electronic shutter, for example it is used in Q cameras

First of all have you seen DOF of medium format? Second have you seen the detail of medium format? Have you ever printed large size? If yes why do you ask?

Have you seen my avatar? Do you realize what camera that is? Yes, I sold several large (over 36") prints last year.

So, how about some questions to you then... Have you ever been hired, for pay, to shoot a wedding? Ever sold a "large" print of the bouquet toss? Have you ever shot medium format? Have you ever carried a MF rig around for an hour or more? Why not large format? The quality and DoF on 4x5 makes medium format look like a cheap Holga. Imagine a 3fps sheet feeder...

I know this: I would much rather use 35mm/APS in a fast moving setting. They're smaller and lighter. In the shot you describe, narrow DOF is the devil you are constantly fighting against. You also need reach so you're not a distracting element - 50mm in APS is equivalent to 120mm on MF, 120mm on APS is 300mm on MF. That's a heavy rig to tote at a wedding.

I didn't pose my question to start a pissing match. I'm curious to hear from people, possessing real-world experience with MF, who actually might have a real-world need for 2+ fps in medium format.

Have you seen my avatar? Do you realize what camera that is? Yes, I sold several large (over 36") prints last year.

So, how about some questions to you then... Have you ever been hired, for pay, to shoot a wedding? Ever sold a "large" print of the bouquet toss? Have you ever shot medium format? Have you ever carried a MF rig around for an hour or more? Why not large format? The quality and DoF on 4x5 makes medium format look like a cheap Holga. Imagine a 3fps sheet feeder...

I know this: I would much rather use 35mm/APS in a fast moving setting. They're smaller and lighter. In the shot you describe, narrow DOF is the devil you are constantly fighting against. You also need reach so you're not a distracting element - 50mm in APS is equivalent to 120mm on MF, 120mm on APS is 300mm on MF. That's a heavy rig to tote at a wedding.

I didn't pose my question to start a pissing match. I'm curious to hear from people, possessing real-world experience with MF, who actually might have a real-world need for 2+ fps in medium format.

That is why I asked. Okay?

First, sorry for being little bit ruder than i should.
Second yes i cared MF rig for several weeks like a street camera. 4x5 is cool, but silver prices a constantly going up so itís harder to push it in my budget .